The invention relates to a method of producing finely-divided, water-insoluble silicates which are capable of cation exchange, and which still contain bound water, of the general formula I: EQU (Na.sub.2 O).sub.0.8-1.3.(Al.sub.2 O.sub.3).(SiO.sub.2).sub.1.75-2.0 (I)
These finely-divided, water-insoluble silicate cation-exchangers of the above formula can be called "aluminosilicates."
These aluminosilicates, optionally also in the form of the suspensions produced, are suitable for further processing and for the production of washing and cleansing agents. The invention, therefore, also relates to the suspensions, obtainable in accordance with the method, and the use thereof, particularly for the production of washing and cleaing agents.
The compounds of general formula I are capable of cation exchange with the hardening constituents of water, that is, magnesium ions and calcium ions. Their calcium binding capacity generally lies above 50 mg CaO/gm of active substance (AS), preferably in the range of from 100 to 200 mg CaO/gm of active substance. The calcium binding capacity can be determined in accordance with the Calcium Binding Power Test Method given in Example 1. The term "active substance" refers to the solid substance obtained by drying for one hour at 800.degree. C. The water-insoluble silicates described above are of particular interrest as contents of washing and cleansing agents, since they are capable of entirely or partially replacing the phosphate builder substances still predominantly used nowadays.
Aluminosilicates of the formula given above, and which are capable of cation exchange, are known. They are generally synthesized by combining solutions of individual components to produce an aqueous synthesizing mixture which mathematically comprises Al.sub.2 O.sub.3 and SiO.sub.2 in the specified ratio, and Na.sub.2 O and water. Solutions of sodium aluminate and sodium silicate usually are utilized as starting components.
A large number of different methods are already available for producing such compounds within the scope given above. Specific examples of synthetic aluminosilicates are disclosed in U.S. Pat. Nos. 2,882,243; 2,962,355; 3,010,789; 3,012,853; 2,882,244 and 3,130,007. In addition, a general method is disclosed in German Published Application (DOS) No. 2,412,837. In this published application, a process for washing, bleaching and cleaning, in particular of textiles, is described where aluminosilicates are used. In the specification text, manufacturing processes for the aluminosilicates used are also specifically stated, especialy on pages 26 and 27. In the procedure there described, the starting solutions are mixed together, then stirred rapidly for ten minutes and after that the mixture is left in a crystallizer for several hours. After washing and drying, the products obtained are finely ground in a ball mill and air sifted to separate the fraction over 10.mu. in particle size. Only when they are in this form, the resulting aluminosilicates are incorporated in detergents (see page 25).
Another method of obtaining finely-divided, water-insoluble aluminosilicates involving a controlled precipitation to avoid formation of a gel structure is described in U.S. Pat. No. 4,041,135.
In addition, commonly-assigned U.S. patent application Ser. No. 765,530, filed Feb. 4, 1977 now abandoned in favor of its continuation Ser. No. 962,906, filed Nov. 22, 1978, now abandoned, describes another method to avoid formation of a gel structure by subjecting the formed aluminosilicate suspension to homogenization by cavitation before crystallization.
Nevertheless, there is still need for a method which, with a short reaction period of the components and a high space-time yield, produces aluminosilicates of the above-mentioned formula which are extremely finely-divided and which, however, have a narrow particle size spectrum or range.